Employee was trying to loosen a 5-1/2' cone crusher after it had blown a hydraulic line going to the clamping system. The employee was using three, 3-ton come-a-longs to turn the bowl and loosen the crusher. As the employee was tightening one of the come-a-longs, it slipped from the rigging and came back and hit the employee in the right leg in the shin breaking the leg.